Subjectively Reported Effects Experienced in an Actively Shielded 7T MRI: A Large‐Scale Study

Abstract

Background Ultrahigh‐field (UHF) MRI advances towards clinical use. Patient compliance is generally high, but few large‐scale studies have investigated the effects experienced in 7T MRI systems, especially considering peripheral nerve stimulation (PNS) and caregiving. Purpose To evaluate the quantity, the intensity, and subjective experiences from short‐term effects, focusing on the levels of comfort and compliance of subjects. Study Type Prospective. Population In all, 954 consecutive MRIs in 801 subjects for 3 years. Field Strength 7T. Assessment After the 7T examination, a questionnaire was used to collect data. Statistical Tests Descriptive statistics, Spearman's rank correlation, Mann–Whitney U‐test, and t‐test. Results The majority (63%) of subjects agreed that the MRI experience was comfortable and 93% would be willing to undergo future 7T MRI as a patient (5% undecided) and 82% for research purposes (12% undecided). The most common short‐term effects experienced were dizziness (81%), inconsistent movement (68%), PNS (63%), headache (40%), nausea (32%), metallic taste (12%), and light flashes (8%). Of the subjects who reported having PNS (n = 603), 44% experienced PNS as “not uncomfortable at all,” 45% as “little or very little uncomfortable,” and 11% as “moderate to very much uncomfortable.” Scanner room temperature was experienced more comfortable before (78%) than during (58%) examinations, and the noise level was acceptable by 90% of subjects. Anxiety before the examination was reported by 43%. Patients differed from healthy volunteers regarding an experience of headache, metallic taste, dizziness, or anxiety. Room for improvement was pointed out after 117 examinations concerning given information (n = 73), communication and sound system (n = 35), or nursing care (n = 15). Data Conclusion Subjectively reported effects occur in actively shielded 7T MRI and include physiological responses and individual psychological issues. Although leaving room for improvement, few subjects experienced these effects being so uncomfortable that they would lead to aversion to future UHF examinations. Level of Evidence 1 Technical Efficacy Stage 5 J. Magn. Reson. Imaging 2020;52:1265–1276.

Claustrophobia—empowering the patient

“…Furthermore, wider and shorter bores, noise reduction, distraction with music and movies during the examination and fast scanning are efforts to increase compliance with MR examinations. In addition, communication skills of personnel performing MR examinations are imperative to create a soothing atmosphere during the examination [7].…”

In vivo investigation of the multi‐exponentialT2decay in human white matter at 7 T: Implications for myelin water imaging at UHF

“…In addition to SENSE acceleration, greater EPI acceleration might be of interest at 7 T. When a shorter Δ TE of 8 ms or an EPI factor of 5 was attempted, peripheral nerve stimulation (PNS) increased to about 80% of the first control level and volunteers reported PNS. The specific gradient coil design may have contributed to the prevalence of PNS 37,38 . Because this can only be alleviated by decreasing in‐plane resolution, sequence adjustments were not further pursued for the sake of comparability.…”

“…The specific gradient coil design may have contributed to the prevalence of PNS. 37,38 Because this can only be alleviated by decreasing in-plane resolution, sequence adjustments were not further pursued for the sake of comparability. Using the traditional parameters (ΔTE = 10 ms, EPI factor = 3), PNS was at 65% of the first control level and none of the subjects reported PNS or a feeling of warmth during GraSE.…”

7T MR Safety

“…A broad range of such activations has been reported (ranging from 30–85% among imaged subjects 3,19 ), most likely due to large variations in magnet design, subject positioning, and/or table speeds. However, surveys conducted postimaging revealed a strong willingness of subjects to undergo repeat imaging, and ancillary evidence of patients imaged clinically at 7T reveal similar levels of tolerance to imaging at lower field strengths 28 . Subjects should be advised to keep their head still at all times, from initial positioning on the table before the exam to removal of the RF coil at the end.…”